1. Field of the Invention
The present invention relates to an image display device that decrypts encrypted video signals and displays the decrypted video signals as an image, and more particularly to an image display device that prevents decrypted video signals from being acquired or copied illegally.
2. Description of the Related Art
Copyright protection of video signals (contents) is very important on a video apparatus, such as an image display device, that processes video signals. A recent digital technology finds many applications in the broadcasting and video fields with more and more digital video signals received by the image display devices of home television sets. An example of digital video signals is baseband digital video signals that are encrypted to prevent an illegal copy. An image display device that processes digital video signals, such as the one described above, has a decryptor that decrypts encrypted video signals and displays them on the display as an image.
An image display device has connectors, wires, or circuit board wirings in its inside that are exposed. Because video signals output from the decryptor are already decrypted, the image display device allows a person to intentionally open the cover of the image display device to illegally take out the decrypted video signals output from the decryptor. Therefore, the problem with this type of image display device is that, unless some countermeasures are taken, the video signals (contents) may be acquired or copied illegally.
One of the ways to prevent the illegal acquisition or illegal copy of video signals is to eliminate exposed parts by protecting the exposed connectors, wires, or wirings inside the image display device to prevent video signals from being taken out. However, this method is not preferable because it decreases the design flexibility of the image display device and increases the cost. In addition, because it is relatively easy to remove the protection of exposed parts to take out video signals, this method does not efficiently prevent an illegal acquisition or an illegal copy.
It is expected that more and more encrypted video signals will be used in the future and that the protection of contents copyrights will become more and more important. Therefore, the copyright protection of encrypted video signals is very important and there is a need for an effective solution.